Chinese ???

[ieezitin]

Here is a little visual on what 1 or 2 deg variance looks like shown in bubble language.


Here you have the shot looking east and showing Zero on the bubble level and zero on the digital level. Notice the .005 shim placed under the digital level.








Now here is the shot looking west, the digital level is showing 2deg and I can assure you the inclinometer is still zero. Notice the shim still under the level.







Now you have the shot showing the digital level with the shim 005 shim removed. It shows 0.1, now if you turn it around 180DEG it would read 0.1Deg. Notice the Inclinometer still reading zero







Now here is a shot of the inclinometer reading level on a level surface.







Now here is a shot with the same 005 shim under it, its banging the needle right!! (its hard to see but the shim is on the left)







Pictures speak a thousand words. This Doo Dad is worth as much as an ashtray on a motorbike.

Anthony.

[ieezitin]

Quote:. Lathes can be set up without them at the expense of time. It takes a couple of hours, starting with a two-collar spindle test in the chuck and then several collars on a long bar between centers. Be warned though - it's not obvious at all, some imagination required. For example, tailstock droop/slop and spindle bearing condition can confound you, but with patience you'll end up averaged for wear, a good thing.

Sunset.

Are you saying to level the lathe by using a turned test bar in the spindle? In a way I see that, you would end up with longitudinal level according to tailstock and headstock, but what about its perpendicular axis? I need a little clarification.

All being said I would have thought seating the bed into true would show up discrepancies on the afore mentioned, where if needed its a lot easier to correct, to put it another way if a bed has wear true it up and mate the headstock and tailstock to the bed if its that bad. Or re-grind the bed.

A little sketch would be handy.

Anthony.

[f350ca]

With the shim under the digital level rotating it would indicate the calibration is out by .1 deg. When you rotate it without the shim does the high side follow the level, if so then again the calibration is out by .1 deg.

[ieezitin]

(01-20-2013, 11:00 AM)f350ca Wrote: With the shim under the digital level rotating it would indicate the calibration is out by .1 deg. When you rotate it without the shim does the high side follow the level, if so then again the calibration is out by .1 deg.

in one way You are a 100% correct. which makes its error .021 thou per ft. expressed that way but consider this, with the shim under the digital level and its reading showing 0.2deg then with the shim taken out it reads 0.1 (both directions)how far from 0.2 did it move?

If for example it just shaves off 0.01 to register its 0.1 reading that would be close to 040 thou per ft, expressed another way 7/16" over ten feet.

i am not a perfectionist dont get me wrong, but its inherent flaws makes it useless in a machine shop. i am hoping a new person to our hobby absorbs this little tutorial on levels.

Anthony.

[f350ca]

Thats pretty much the case with any measuring instrument. The best you can hope for is plus or minus the tolerance or its smallest reading.
For levelling a lathe you need something like the one at the top, the lower one is sensitive but doesn't have the accuracy noted on it.


When I use that one I never rotate it, level doesn't matter it twist your looking to remove. Error in the level doesn't matter then, just sensitivity.

[TomG]

According to the Home Depot website, that digital level is only accurate to 1/10 degree, so it's doing what it's supposed to do. A typical bubble machinists level like you would get from Starrett for instance, is accurate to .005in/ft. or .02º, an order of ten better. Comparing one to the other would be like trying to use a ruler to measure something that you would normally measure with a micrometer. Save the digital level for hanging pictures and keep the bubble level in your shop.

Tom